Various aqueous systems contain microorganisms which exhibit either aerobic or anaerobic metabolic activity. The presence of these microorganisms may result from natural conditions, such as would occur from the normal multiplication of microbes in aqueous environments, or from the accidental introduction of microbes, such as sulfate-reducing bacteria (SRB) found in the oil processing industry.
The unchecked proliferation of the microbial population results in numerous unacceptable conditions, such as odor problems, safety hazards (from H.sub.2 S generation), the buildup of excessive deposits and the fouling of processing equipment in contact with the aqueous medium. In order to prevent these problems, antimicrobial chemical agents are utilized to control the growth of the microbes.
Aerobic and anaerobic microorganisms having a respiratory metabolism biochemically oxidize either organic or inorganic chemical compounds in order to obtain energy for growth and reproduction. These are enzymatically mediated chemical oxidations and must be coupled with chemical reductions in order for the reactions to continue. This process is actually a series of oxidation/reduction steps culminating in a terminal reduction reaction which balances the initial oxidation reaction. The terminal reduction is usually that of the reduction of O.sub.2 to H.sub.2 O in aerobes and may be a number of reactions in anaerobes (e.g., SO.sub.4.sup..dbd. .fwdarw.H.sub.2 S for some sulfate reducing bacteria, such as Desulfovibrio).
Oxidizing and non-oxidizing antimicrobials affect microorganisms in many various modes of action which usually have little to do with inhibiting the terminal reduction reaction. It has been discovered, in accordance with the present invention, that the addition of compounds capable of competing with the compound normally used by a microorganism as its terminal electron acceptor slows the biochemical reduction process by virtue of this competition for the electrons generated by the substrate oxidations.
The efficiency of these compounds as a competing terminal oxidant may vary and perhaps may even be less efficient than the usual terminal oxidant. Nonetheless, regardless of the degree of efficiency of the terminal oxidant, the ability of the microorganism to generate cellular energy such as ATP, is severely affected. An antimicrobial added to the system would have greater efficacy against a weakened group of microorganisms laboring in an environment concentrated with compounds competing for the available electrons.